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bioRxiv · 10.1101/2022.10.11.511808

Stochastic chain termination in bacterial pilus assembly

Giese, C.·Puorger, C.·Ignatov, O.·Becarova, Z.·Weber, M.·Scharer, M.·Capitani, G.·Glockshuber, R.
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Abstract

Adhesive type 1 pili from uropathogenic Escherichia coli strains are filamentous, supramolecular protein complexes consisting of a short tip fibrillum and a long, helical rod formed by up to several thousand copies of the major pilus subunit FimA. Here, we reconstituted the entire type 1 pilus rod assembly reaction in vitro, using all constituent protein subunits in the presence of the assembly platform FimD, and identified the so-far uncharacterized subunit FimI as an irreversible assembly terminator. We provide a complete, quantitative model of pilus rod assembly kinetics based on the measured rate constants of FimD-catalyzed subunit incorporation. The model reliably predicts the length distribution of assembled pilus rods as a function of the ratio between FimI and the main pilus subunit FimA and is fully consistent with the length distribution of membrane-anchored pili assembled in vivo. The results show that the natural length distribution of adhesive pili formed via the chaperone-usher pathway results from a stochastic chain termination reaction.

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Giese, C., Puorger, C., Ignatov, O., Becarova, Z., Weber, M., Scharer, M., Capitani, G., Glockshuber, R.. 2022-10-12. Stochastic chain termination in bacterial pilus assembly. https://doi.org/10.1101/2022.10.11.511808

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